The conversion rates of marketing email campaigns increased by more than 11 percent in the fourth quarter of last year, and by more than 16 percent in all of 2010, according to a new study sponsored by Epsilon, a multi-channel marketing service.

For the study, titled "Q4 2010 Email Trends and Benchmarks," researchers analyzed the 7.4 billion emails that Epsilon sent out on behalf of 150 participating clients between October and December of 2010. They found that the open rates of marketing emails improved by 5 percent in the last two years, with four of 13 industries recording an increase over their 2009 numbers.

Click rates remained static over the last two years, but dropped from 5.9 percent to 5.1 percent in the last 12 months alone. The non-bounce back rate experienced a small jump from 93.9 percent to 95 percent over the past year, while the average volume per client rose 18.5 percent in the same period.

However, the increase in email marketing conversion rates is what really stood out. The overall conversion rate of 2.9 percent for the quarter was the highest in the last two years.

When breaking it down for specific industries, the consumer products group may have experienced the greatest level of success. This subset of companies had an overall click rate of 10.3 percent, the highest among any North American industry that was accounted for in the survey. Furthermore, consumer products companies boasted a 53.7 percent click to open rate, by far the best among all 13 industries.

The travel and hospitality travel services industry sported the highest click rate of 28.4 percent. Service and editorial messages, which are usually targeted for specific consumers based on their preferences, had much better open and click rates compared to general marketing messages.